Upshift control for regenerative braking

Abstract

A vehicle includes a powertrain and a controller. The powertrain includes a transmission mechanically coupled to an electric machine and configured to transfer torque between a wheel and the electric machine. The transmission has a gearbox configured to establish gear ratios through a shift. The controller is programmed to, in response to an indication of an expected regenerative braking event having a timing falling within a shift window of the transmission, prevent a clutch of the transmission from disengaging until first occurrence of application of an accelerator pedal or removal of the indication to inhibit the shift prompted by a shift schedule of the gearbox.

What is claimed is: 
     
       1. A vehicle comprising:
 a controller programmed to, in response to release of an accelerator pedal and an indication of an expected regenerative braking event having a timing falling within a transmission upshift time window, prevent a clutch of a transmission from disengaging until first occurrence of reapplication of the accelerator pedal or removal of the indication, to inhibit a transmission upshift prompted by the release when an anticipated gear ratio resulting from the upshift is predicted to decrease a speed of a generator shaft below a constant power region of a generator. 
 
     
     
       2. The vehicle of  claim 1 , wherein the speed is less than a base speed of the generator. 
     
     
       3. The vehicle of  claim 1 , wherein the preventing is further in response to an anticipated gear ratio resulting from the upshift being predicted to result in a wheel torque associated with an estimated regenerative brake torque of the event transcending a generating power limit of a generator. 
     
     
       4. The vehicle of  claim 3 , wherein the wheel torque is limited by a proportional relationship to a constant power region of the generator. 
     
     
       5. The vehicle of  claim 3 , wherein the estimated regenerative braking torque is based on a difference between an average road grade and a current road grade. 
     
     
       6. The vehicle of  claim 3 , wherein the estimated regenerative braking torque is based on a headway range and a rate of change thereof. 
     
     
       7. The vehicle of  claim 3 , wherein the estimated regenerative braking torque is based on a predicted deceleration rate. 
     
     
       8. The vehicle of  claim 1 , wherein presence of the expected regenerative braking event is based on a difference between an average road grade and a current road grade. 
     
     
       9. The vehicle of  claim 8 , wherein the average road grade has a period that begins with the release. 
     
     
       10. The vehicle of  claim 1 , wherein presence of the expected regenerative braking event is based on an adaptive cruise control headway range. 
     
     
       11. The vehicle of  claim 10 , wherein presence of the expected regenerative braking event further is based on a rate of change of the adaptive cruise control headway range. 
     
     
       12. The vehicle of  claim 1 , wherein presence of the expected regenerative braking event is based on a predicted deceleration rate. 
     
     
       13. The vehicle of  claim 12 , wherein presence of the expected regenerative braking event further is based on a difference between an average deceleration rate and the predicted deceleration rate. 
     
     
       14. A method comprising:
 responsive to release of an accelerator pedal and indication of an expected regenerative braking event having a timing falling within a transmission upshift window, preventing by a controller a clutch of a transmission from disengaging until reapplication of the accelerator pedal, to inhibit a transmission upshift prompted by the release when an anticipated gear ratio upshift is predicted to decrease generator shaft speed below a constant power region of a generator. 
 
     
     
       15. A vehicle comprising:
 a powertrain including a transmission mechanically coupled to an electric machine and configured to transfer torque between a wheel and the electric machine, the transmission having a gearbox configured to establish gear ratios through a shift; and 
 a controller programmed to, in response to an indication of an expected regenerative braking event having a timing falling within a shift window of the transmission, prevent a clutch of the transmission from disengaging until first occurrence of application of an accelerator pedal or removal of the indication, to inhibit the shift prompted by a shift schedule of the gearbox when an anticipated gear ratio resulting from the shift is predicted to decrease a speed of a shaft of the electric machine below a constant power region of the electric machine. 
 
     
     
       16. The vehicle of  claim 15 , wherein the shift window is based on an average shift time of the gearbox. 
     
     
       17. The vehicle of  claim 15 , wherein the speed is less than a base speed of the electric machine. 
     
     
       18. The vehicle of  claim 15 , wherein the preventing is further in response to an anticipated gear ratio resulting from the shift being predicted to result in a wheel torque associated with an estimated regenerative brake torque of the event transcending a generating power limit of the electric machine.